Magnetic wall utilization-analog memory element and magnetic wall utilization analog memory

ABSTRACT

A magnetic wall utilization-analog memory element includes a magnetic wall driving layer including a magnetic wall, a first region, a second region, and a third region located between the first region and the second region, a magnetization fixed layer provided at a the third region through a nonmagnetic layer, and a lower electrode layer provided at a position in the third region that overlaps the magnetization fixed layer in plan view on a second surface opposite to a first surface on which the magnetization fixed layer is provided.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent application Ser. No. 16/060,042, filed Jun. 7, 2018, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a magnetic wall utilization-analog memory element and a magnetic wall utilization analog memory.

Priority is claimed on Japanese Patent Application No. 2016-085530 filed in Japan on Apr. 21, 2016, the contents of which are incorporated herein by reference.

BACKGROUND ART

As a next-generation nonvolatile memory substituting for a flash memory or the like which has come to have a limit in miniaturization, a resistance change memory for storing data by using a resistance variable element, such as MRAM (Magnetoresistive Random Access Memory), ReRAM (Resistance Random Access Memory), PCRAM (Phase Change Random Access Memory), and the like has attracted attention.

As a method of increasing the memory density (increasing capacity), there is a method of reducing the size of the elements constituting the memory, as well as a method of multileveling the recording bits per element constituting the memory, and various multileveling methods have been proposed (for example, see Patent Documents 1 to 3).

There is one type of MRAM called a magnetic wall driving type or a magnetic wall shifting type (for example, see Patent Document 4). The magnetic wall driving MRAM allows current to flow in an in-plane direction of a magnetic wall driving layer (or magnetization free layer), shifts the magnetic wall by the spin transfer effect of spin polarized electrons, and reverses the magnetization direction of the ferromagnetic film according to the direction of the write current and writes data.

Patent Document 4 describes a method of multilevel recording and analog recording with respect to a magnetic wall driving MRAM.

In MRAM, different writing methods of data have been proposed, and in addition to a magnetic wall driving MRAM, a magnetic field writing MRAM, a yoke magnetic field writing MRAM, an STT (Spin Transfer Torque) MRAM, an SOT (Spin Orbit Torque) MRAM, and the like are known.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2015-088669

[Patent Document 2] International Publication No. 2009/072213

[Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2016-004924

[Patent Document 4] International Publication No. 2009/101827

[Patent Document 5] International Publication No. 2009/054180

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In the conventional magnetic wall driving MRAM, it is necessary to flow a current in the in-plane direction of the magnetic wall driving layer (or the magnetization free layer) at the time of reading, so that the magnetic wall of the magnetic wall driving layer may shift due to the current flowing at the time of reading. When the magnetic wall shifts outside the portion where the magnetic wall driving layer and the magnetoresistive effect element overlap, the signal finally becomes a digital signal of 0 or 1 in the magnetic wall driving MRAM, and it is difficult to use the magnetic wall driving MRAM as an analog memory.

Conversely, if the magnetic wall shift is not completed outside the portion where the magnetic wall driving layer (or the magnetization free layer) and the magnetoresistance effect element overlap, the magnetic wall shifts during reading to erroneously write or read out initial signal changes. That is, in the conventional magnetic wall driving MRAM, there is no way to stably read data even if data can be written in a multivalued or analog manner. If the data written analogically can be read stably, it is possible to stably read data written in a multilevel manner.

The present invention has been made in view of the above circumstances, and provides a magnetic wall utilization-analog memory element and a magnetic wall utilization analog memory capable of stably reading out the analog recording data.

Means for Solving the Problems

A first aspect of the present invention is a magnetic wall utilization-analog memory element which includes a magnetic wall driving layer including a magnetic wall, a first region, a second region, and a third region located between the first region and the second region, a magnetization fixed layer provided at a the third region through a nonmagnetic layer, and a lower electrode layer provided at a position in the third region that overlaps the magnetization fixed layer in plan view on a second surface opposite to a first surface on which the magnetization fixed layer is provided.

A second aspect of the present invention is the magnetic wall utilization-analog memory element according to the first aspect, which may further include a high resistance layer between the magnetic wall driving layer and the lower electrode layer.

A third aspect of the present invention is the magnetic wall utilization-analog memory element according to the first or second aspect, where a length of the magnetic wall driving layer may be 60 nm or more.

A fourth aspect of the present invention is the magnetic wall utilization-analog memory element according to any one of the first to third aspect, which may further include a first magnetization supply layer which is in contact with the first region and has a first magnetization direction, and a second magnetization supply layer which is in contact with the second region and has a second magnetization direction opposite to the first magnetization direction.

A fifth aspect of the present invention is the magnetic wall utilization-analog memory element according to the fourth aspect, where the first magnetization supply layer, the second magnetization supply layer, and the magnetization fixed layer may be parallel to each of the corresponding layers.

A sixth aspect of the present invention is the magnetic wall utilization-analog memory element according to the fourth aspect, where a magnetization orientation of each of the magnetic wall driving layer, the first magnetization supply layer, the second magnetization supply layer, and the magnetization fixed layer may be perpendicular to each of the corresponding layers.

A seventh aspect of the present invention is the magnetic wall utilization-analog memory element according to any one of the first to sixth aspect, where the magnetic wall driving layer may have a magnetic wall pinning portion.

An eighth aspect of the present invention is the magnetic wall utilization-analog memory element according to any one of the fourth to seventh aspect, where a bipolar element may be connected to either one of the first magnetization supply layer and the second magnetization supply layer.

A ninth aspect of the present invention is a magnetic wall utilization analog memory including a plurality of magnetic wall utilization analog memory elements according to any one of the first to eighth aspects.

A tenth aspect of the present invention is the magnetic wall utilization analog memory according to ninth aspect, which may include a mechanism reading a resistance change between the lower electrode layer and the magnetization fixed layer at the time of reading.

An eleventh aspect of the present invention is a volatile logic circuit including a magnetic wall utilization analog memory on which the magnetic wall utilization-analog memory element according to any one of the first to eighth aspects, and an STT-MRAM, where the circuit has a memory function and a logical function, and as the memory function, includes the magnetic wall utilization analog memory and the STT-MRAM.

A twelfth aspect of the present invention is a magnetic neuro element including the magnetic wall utilization-analog memory element according to any one of the first to eighth aspects, where the third region of the magnetic wall driving layer includes a first memory portion, and the second memory portion and a third memory portion arranged so as to sandwich the first memory portion therebetween, which are arranged side-by-side in the longitudinal direction, and the magnetic neuro element includes a current source having a control circuit which is controllable of a flow of a write current capable of shifting magnetic walls sequentially such that the magnetic walls remain in all the memory portions of the first memory portion, the second memory portion, and the third memory portion at least once.

Effects of the Invention

According to the aspects of the present invention described above, it is possible to stably read multilevel recording data or analog recording data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an example of a magnetic wall utilization analog memory element according to one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of another example of a magnetic wall utilization analog memory element according to one embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of a conventional domain wall drive magnetoresistance effect element.

FIG. 4A is a schematic cross-sectional view describing a method of shifting a magnetic wall in a conventional magnetic wall driving magnetoresistive effect element.

FIG. 4B is a schematic cross-sectional view describing a method of shifting a magnetic wall that shifts a magnetic wall in a direction opposite to that of FIG. 4A.

FIG. 5 is a schematic cross-sectional view describing a path through which read current flows in a conventional magnetic wall driving magnetoresistance effect element.

FIG. 6 is a schematic cross-sectional view describing a path through which read current flows in the magnetic wall utilization-analog memory element of the present invention.

FIG. 7 is a cross-sectional schematic view describing the principle of writing and reading of the magnetic wall utilization-analog memory element of the present invention.

FIG. 8 is a graph conceptually showing a relationship between the proportion of the area of the portion parallel to the magnetization direction of the magnetization fixed layer and the resistance value of the magnetoresistance effect element portion.

FIG. 9 is a cross-sectional view of a main portion of a cell in a magnetic wall utilization analog memory of the present invention.

FIG. 10 is a diagram schematically showing an example of a circuit structure of a magnetic wall utilization analog memory of the present invention.

FIG. 11 is a schematic cross-sectional view of another example of a magnetic wall utilization-analog memory element according to one embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view of another example of a magnetic wall utilization-analog memory element according to one embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view of an example of a magnetic neuro element according to an embodiment of the present invention.

FIG. 14 is a diagram showing an artificial brain concept using a magnetic neuro element according to an embodiment of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, the configuration of the magnetic wall utilization-analog memory element and the magnetic wall utilization analog memory to which the present invention is applied will be described with reference to the drawings. In the drawings used in the following description, for the sake of easy understanding of the features, the characteristic portions are sometimes enlarged for convenience, and the dimensional ratios of the respective components are not always the same. In addition, the materials, dimensions, and the like exemplified in the following description are mere examples, and the present invention is not limited thereto, and it is possible to carry out the present invention by appropriately changing and modifying it within a range that achieves the effects of the present invention. In the element of the present invention, other layers may be provided as long as the effect of the present invention is achieved.

(Magnetic Wall Utilizing-Analog Memory Element)

FIG. 1 is a cross-sectional view schematically showing an example of a magnetic wall utilization-analog memory element according to one embodiment of the present invention.

The magnetic wall utilization-analog memory element 100 shown in FIG. 1 has a magnetic wall driving layer 1 having a magnetic wall DW and including a first region 1 a, a second region 1 b, and a third region 1 c disposed therebetween. The magnetic wall utilization-analog memory element 100 further includes a lower electrode layer 4 which is in contact with a third region and a magnetization fixed layer 5 provided at an opposite surface of a surface of the third region that is contact with the lower electrode layer 4 via a nonmagnetic layer 6.

The magnetic wall utilization-analog memory element 100 shown in FIG. 1 further includes a first magnetization supply layer 2 which is in contact with the first region 1 a and has a first magnetization direction, and a second magnetization supply layer 3 which is in contact with the second region and has a second magnetization direction opposite to the first magnetization direction. When the first magnetization supply layer 2 and the second magnetization supply layer 3 are not provided, the write current flowing into the magnetic wall driving layer 1 can be a spin polarized current.

In addition, the magnetic wall utilization-analog memory element 100 shown in FIG. 1 further includes a high resistance layer 7 between the magnetic wall driving layer 1 and the lower electrode layer 4. The high resistance layer 7 has higher electrical resistivity than the magnetic wall driving layer 1. The high resistance layer 7 is a layer preventing current from flowing into the lower electrode layer 4 when driving the magnetic wall of the magnetic wall driving layer 1 to inhibit the magnetic wall driving. The material of the high resistance layer 7 is not particularly limited as long as it is a material that performs the prevention function described above. It may be a nonmagnetic material. The high resistance layer 7 may be a tunnel barrier layer. Therefore, the high resistance layer 7 may be an insulating material that allows tunnel current to flow therethrough.

In FIG. 1, the stacking direction of each layer, that is, the direction orthogonal to the main surface of each layer (perpendicular direction to the surface) is defined as the Z direction. Each layer is formed parallel to the XY plane orthogonal to the Z direction.

A magnetization fixed layer is a layer in which a magnetization direction does not change (magnetization is fixed) before or after writing using the write current, and any layers satisfied such a condition can be used without limitation.

The magnetization free layer 1 is a magnetization free layer formed of a ferromagnetic material, and the magnetization direction thereof can be reversed. The magnetization free layer 1 has a magnetic wall, and by flowing current equal to or more than a threshold value in a direction (X direction) passing through the magnetic wall, by the spin polarized current generated in the domain (magnetic domain) of the magnetic wall driving layer 1, it is possible to shift the magnetic wall in the direction in which conduction electrons flow.

The first magnetization supply layer 2, the second magnetization supply layer 3, and the magnetization fixed layer 5 are layers (ferromagnetic layers) formed of a ferromagnetic material whose magnetization is fixed. The first magnetization supply layer 2 and the second magnetization supply layer 3 are arranged to face the magnetization fixed layer 5 with the magnetic wall driving layer 1 interposed therebetween. In addition, the first magnetization supply layer 2 and the second magnetization supply layer 3 are magnetically coupled to the magnetic wall driving layer 1. At the time of data writing, write current is flowed from one end to the other end of the magnetic wall driving layer 1.

In FIG. 1, the arrow M1, the arrow M2, and the arrow M3 indicate the magnetization direction of each layer, and the arrows M4 and M5 respectively indicate in the magnetic wall driving layer 1, the magnetization direction of a portion on the side of the first magnetization supply layer 2 with the magnetic wall DW as a boundary and the magnetization direction of a portion on the side of the second magnetization supply layer 3 with the magnetic wall DW as a boundary.

In the examples shown in FIG. 1, the magnetic wall driving layer 1, the first magnetization supply layer 2, the second magnetization supply layer 3, and the magnetization fixed layer 5 are magnetization films having in-plane magnetic anisotropy (axis of easy in-plane magnetization). However, as shown in FIG. 2, these layers may be perpendicular magnetization films having perpendicular magnetic anisotropy (axis of easy perpendicular magnetization). As a material which is easy to form an in-plane magnetization film, for example, NiFe is available. Further, as a film which easily forms a perpendicular magnetization film, for example, a Co/Ni laminated film is available.

When an in-plane magnetization film is used, an MR ratio is high and it is difficult to write by STT at the time of reading, so that large reading voltage can be used. On the other hand, when it is desired to miniaturize the element, it is preferable to use a perpendicular magnetization film having large magnetic anisotropy and small demagnetizing field. Since resistance to thermal disturbance is large, it is difficult to erase data.

Hereinbelow, a principle of stably writing and reading the data of a magnetic wall utilization-analog memory element of the present embodiment is described.

Compared to each element of the conventional magnetic wall driving MRAM, in a magnetic wall utilization-analog memory element of the present embodiment, since a driving wall shift when the reading is remarkably prevented, stable analogue data output which cannot be realized in the conventional magnetic wall driving MRAM can be obtained.

Here, a conventional magnetic wall driving MRAM will be described.

The MRAM has a magnetoresistance effect element utilizing a magnetoresistive effect such as a GMR (Giant Magneto Resistance) effect and a TMR (Tunnel Magneto Resistance) effect as a memory cell. The magnetoresistance effect element has, for example, a laminated structure in which two ferromagnetic layers are laminated via a nonmagnetic layer. The two ferromagnetic layers are a magnetization fixed layer (pinned layer) in which the magnetization direction is fixed and a magnetization free layer (free layer) in which the magnetization direction can be reversed. The value of the electric resistance of the magnetoresistance effect element is larger when the magnetization directions of the magnetization fixed layer and the magnetization free layer are antiparallel than when the magnetization direction is parallel to each other. In the magnetoresistance effect element which is the memory cell of the MRAM, by utilizing the difference in the value of the electric resistance, by associating the parallel state of magnetization with data “0” and the antiparallel state with data “1”, the data is stored in a nonvolatile manner. Reading of data is performed by causing read current to flow through the magnetoresistance effect element (passing through the laminated structure) and measuring the resistance value of the magnetoresistance effect element. On the other hand, data writing is performed by flowing a spin polarized current to invert the magnetization direction of the magnetization free layer.

As the mainstream current data writing method, an “STT method” utilizing spin transfer torque is known. In the STT method, spin polarized current is injected into the magnetization free layer, and torque is generated in the magnetization free layer by the interaction between the spin of conduction electrons responsible for the spin polarized current and the magnetic moment of the magnetization free layer. When the torque is sufficiently large, the magnetization is reversed. Since the magnetization inversion tends to occur as the current density is larger, the write current can be reduced as the size of the memory cell is reduced.

In addition, as the STT method, there has been known a method in which write current flows so as to pass through a magnetoresistive effect element (for example, Patent Document 1) and a method in which write current flows in the in-plane direction of the magnetization free layer without passing through the magnetoresistive effect element (for example, Patent Document 4).

According to the former method, spin-polarized electrons having the same spin state as the magnetization fixed layer are supplied from the magnetization fixed layer to the magnetization free layer, or are extracted from the magnetization free layer to the magnetization fixed layer. As a result, the magnetization of the magnetization free layer is reversed by the spin transfer effect. As described above, the magnetization direction of the magnetization free layer can be defined by the direction of the write current passing through the magnetoresistance effect element. A magnetic wall driving magnetic memory including a plurality of magnetoresistance effect elements described above is called magnetic wall driving MRAM.

On the other hand, the latter method will be described with reference to FIG. 3. FIG. 3 is a schematic cross-sectional view showing an example of a conventional magnetic wall driving magnetoresistance effect element, and compared to a configuration of the magnetic wall utilization-analog memory element shown in FIG. 1, it is different in not including the lower electrode layer 4 and the high resistance layer 7

In the conventional magnetic wall driving magnetoresistance effect element shown in FIG. 3, data writing is performed by shifting the magnetic wall DW formed in the magnetization free layer 11. The magnetization free layer 11 has a first region 11 a and a second region 11 b whose magnetizations are fixed substantially antiparallel to each other and a third region 11 c located between the first region 11 a and the second region 11 b. The magnetization of the third region 11 c is substantially parallel to either the first region 11 a and the second region 11 b. Due to this restriction of the magnetization state, the magnetic wall is introduced into the magnetization free layer 11. The magnetic wall can be shifted by flowing spin polarized current in the magnetization free layer 11.

For example, when current is caused to flow from the second magnetization supply layer 3 to the magnetization free layer 11 and further to the first magnetization supply layer 2 in the direction indicated by the dotted line in FIG. 4A, the conduction electrons flows in the direction indicated by solid lines opposite to the direction of the flow of the current. When the electrons enter the magnetization free layer 11 from the first magnetization supply layer 2, the electrons become spin-polarized electrons, which correspond to the magnetization direction of the domain magnetically coupled to the first magnetization supply layer 2 and the first magnetization supply layer 2 of the magnetization free layer 11. When the spin-polarized electrons reach the magnetic wall, the spin of the spin-polarized electrons in the magnetic wall causes spin transfer with respect to the magnetic wall, and the magnetic wall shifts in the same direction as the flowing direction of the conduction electrons. Likewise, when current is caused to flow from the first magnetization supply layer 2 to the magnetization free layer 11 and further to the second magnetization supply layer 3 in the direction indicated by the dotted line in FIG. 4B, the conduction electrons flows in the direction shown in a solid line opposite to the direction of the flow of the current. When electrons enter the magnetization free layer 11 from the second magnetization supply layer 3, the electrons become spin-polarized electrons, which correspond to the magnetization direction of the domain magnetically coupled to the second magnetization supply layer 3 and the second magnetization supply layer 3 of the magnetization free layer 11. When the spin-polarized electrons reach the magnetic wall, the spin of the spin-polarized electrons in the magnetic wall causes spin transfer with respect to the magnetic wall, and the magnetic wall shifts in the same direction as the flowing direction of the conduction electrons.

By such shift of the magnetic wall, the magnetization of the portion of the magnetization free layer 11 just under the magnetization fixed layer 5 can be set in a state parallel or antiparallel to the magnetization direction of the magnetization fixed layer 5. Therefore, information can be rewritten between the “0” state and the “1” state.

In reading data, current is caused to flow between the magnetization fixed layer 5 and the magnetization free layer 11 via the nonmagnetic layer 6, and a change of resistance corresponding to the relative angle between the magnetization of the magnetization fixed layer 5 and the magnetization of the magnetization free layer 11 is detected. When the magnetization of the portion of the magnetization free layer 11 directly below the magnetization fixed layer 5 is parallel to the magnetization direction of the magnetization fixed layer 5, the resistance is low, whereas when it is antiparallel, the resistance is high. By detecting such a change of resistance, the data is identified.

In the conventional MRAM using the magnetic wall driving magnetoresistive effect element, the data write current does not pass through the magneto-resistive effect element (in FIG. 3, the laminate structure including the magnetization fixed layer 5 and the magnetization free layer 11 via the nonmagnetic layer 6) and flows to the in-plane direction (direction parallel to stacking direction) of the magnetic wall driving layer (see FIGS. 4A and 4B). On the other hand, the data reading current passes through the magnetoresistance effect element (the laminated structure composed of the magnetization fixed layer 5 and the magnetization free layer 11 with the nonmagnetic layer 6 interposed therebetween) as shown by the alternate long and short dash line in FIG. 5, and then flows through a portion of the path through which the write current flows (see, for example, Patent Document 5). That is, the path of the read current partially overlaps the path of the write current.

As described above, in a configuration of the conventional magnetic wall driving MRAM, it is necessary to flow a current in the direction of magnetic wall driving (in-plane direction) of the magnetic wall driving layer (magnetization free layer) at the time of reading. Therefore, the output signal obtained finally becomes a digital signal of 0 or 1. In addition, if the magnetic wall shift is not completed outside the portion where the magnetic wall driving layer (magnetization free layer) and the magnetoresistance effect element portion overlap in plan view, the magnetic wall shifts at the time of reading, and the erroneous writing and the signal change at the initial stage of reading occur.

In contrast, the magnetic wall utilization-analog memory element of the present embodiment includes a lower electrode layer at a position overlapping a magnetization fixed layer which configures a magnetoresistance effect element in plan view. Therefore, the read current flows in a vertical direction of the surface of the magnetization driving layer (magnetization free layer) as shown in the two-dot chain line as shown in FIG. 6. Therefore, since the read current does not flow in the magnetic wall driving direction (in-plane direction) of the magnetic wall driving layer, the shift of the magnetic wall at the time of reading can be reduced. In addition, since the distance of the magnetic wall driving layer through which the read current flows is short, magnetic noise can be reduced.

FIG. 7 is a schematic cross-sectional view showing a case where the magnetic wall DW is positioned in a portion 1 cA between the lower electrode layer 4 and the magnetization fixed layer 5 as well as the nonmagnetic layer 6 and in plan view. The tunnel barrier layer 7 and the lower electrode layer 4 are not shown in FIG. 7.

The magnetic wall DW can be shifted by causing a write current (spin polarized current) to flow in the in-plane direction of the magnetic wall driving layer 1.

The shift direction of the magnetic wall DW can be set depending on the direction in which the write current (spin polarized current) flows. That is, when it is desired to shift the magnetic wall DW in the −X direction, a write current (spin polarized current) is caused to flow in the X direction so that the flow of the spin-polarized electrons strikes from the right side of the magnetic wall DW (see FIG. 4B). Conversely, when it is desired to shift the magnetic wall DW in the X direction, a write current (spin polarized current) is caused to flow in the −X direction so that the flow of the spin-polarized electrons strikes from the left side of the magnetic wall DW (see FIG. 4A).

In addition, the amount of shift (shift distance) of the magnetic wall DW can be variably controlled by adjusting the magnitude and time of the write current. The magnitude and time of the write current may be set, for example, by the number of pulses or the pulse width.

As described above, the position of the magnetic wall DW in the magnetic wall driving layer 1 can be shifted to a desired position by adjusting the direction, magnitude, time, pulse number or pulse width of the write current (spin polarized current) to flow.

When the magnetization fixed layer 5 and the nonmagnetic layer 6 have a same size in plan view and the width W of the X direction thereof is the same as the width of the X direction of the lower electrode layer, a magnetoresistance effect element (hereinafter, may be referred to as “magnetoresistance effect element portion”) 10 is formed by the magnetization fixed layer 5, the nonmagnetic layer 6, and a portion 1 cA of the magnetic wall driving layer 1 that substantially overlaps with the magnetization fixed layer 5 and the nonmagnetic layer 6 in plan view. In the magnetoresistance effect element portion 10, the resistance value varies depending on the position of the magnetic wall DW.

When the magnetic wall DW is at the position shown in FIG. 7, the magnetoresistance effect element portion 10 includes a parallel circuit which includes a low resistance portion, which is formed by the magnetization fixed layer 5, the nonmagnetic layer 6, and a portion 1 cb which is at the side of the second magnetization supply layer 3 from the magnetic wall DW of the magnetic wall driving layer 1 (a portion whose magnetization direction is parallel to the magnetization direction of the magnetization fixed layer 5), and a high resistance portion which is formed by the magnetization fixed layer 5, the nonmagnetic layer 6, and a portion 1 ca which is at the side of the first magnetization supply layer 2 from the magnetic wall DW of the magnetic wall driving layer 1 (a portion whose magnetization direction is antiparallel to the magnetization direction of the magnetization fixed layer 5).

With the above configuration, an analog resistance value can be output as the resistance value of the magnetoresistance effect element portion 10. By setting the position of the magnetic wall DW at a plurality of positions, it is possible to output multivalued resistance values according to the number of the positions.

FIG. 8 is a graph conceptually showing the relationship between the ratio of the area of the portion 1 cb (corresponding to the position of the magnetic wall DW) parallel to the magnetization direction of the magnetization fixed layer 5 and the resistance value of the magnetoresistance effect element portion 10.

Conventionally, there has been a method of setting a multi-valued resistance value or an analog resistance value by shifting the position of the magnetic wall in the magnetic wall driving layer to a desired position; however, there is no method to stably read out the values.

In the magnetic wall utilization-analog memory element of the present embodiment, by providing a lower electrode layer into which the read current flows directly below the magnetization fixed layer 5, it is possible to flow the read current in the vertical direction of the magnetic wall driving layer. That is, by flowing read current (flow of spin-polarized electrons) in a direction parallel to the magnetic wall, it is possible to dramatically reduce the influence on the magnetic wall at the time of reading, as compared with the conventional technique. As a result, stable reading can be performed as compared with the prior art.

As the material of the magnetic wall driving layer 1, a known material that can be used for the magnetization free layer can be used. Particularly, soft magnetic materials can be applied. For example, metals selected from the group consisting of Cr, Mn, Co, Fe and Ni, alloys containing at least one of these metals, and alloys including these metals and at least one element of B, C, and N or the like can be used. Specifically, Co—Fe, Co—Fe—B, and Ni—Fe can be mentioned.

It is preferable that the length of the magnetic wall driving layer 1, that is, the combined length of the first region, the second region, and the third region located between the first and second regions, is preferably 60 nm or more. Usually, when it is less than 60 nm, it tends to be a single magnetic domain and it has no magnetic wall in some cases.

The thickness of the magnetic wall driving layer 1 is not particularly limited as long as it functions as a magnetic wall driving layer; however, it can be 2 to 60 nm, for example. When the thickness of the magnetic wall driving layer 1 is 60 nm or more, magnetic walls may be formed in the stacking direction. However, whether or not the magnetic wall can be formed in the stacking direction is caused by the balance with the shape anisotropy of the magnetic wall driving layer; therefore, when the thickness of the magnetic wall driving layer 1 is less than 60 nm, the magnetic is not be formed.

The magnetic wall driving layer 1 may have a magnetic pinning portion for stopping the shift of the magnetic wall on the side face of the layer. As a specific configuration of the magnetic pinning portion, a well-known structure, for example, irregularities, grooves, bulges, constricted portions, notches, or the like can be used. By providing such a magnetic pinning portion, the magnetic wall can be stopped (pinned), and unless current equal to or larger than the threshold value is passed, the magnetic wall cannot be shifted any more. With the above configuration, the output signal can be multi-leveled instead of analog.

For example, by forming the magnetic pinning portion at predetermined distances, it is possible to more stably hold the magnetic wall, to enable stable multilevel recording, and to read out the multilevel output signal more stably.

For the material of the magnetization fixed layer 5, a known material that can be used for the magnetization fixed layer can be used. For example, metals selected from the group consisting of Cr, Mn, Co, Fe and Ni, alloys containing at least one of these metals, and alloys including these metals and at least one element of B, C, and N or the like can be used. Specifically, Co—Fe and Co—Fe—B can be mentioned.

In order to obtain higher output, Heusler alloys such as Co₂FeSi is preferably used. The Heusler alloy includes an intermetallic compound having a chemical composition of X₂YZ, where X is a transition metal element or a noble metal element of the Co, Fe, Ni, or Cu group on the periodic table, Y is a transition metal of the Mn, V, Cr, or Ti group and can employ element species of X, and Z is a typical element of group III to group V. For example, Co₂FeSi, Co₂MnSi, Co₂Mn_(1-a)Fe_(a)Al_(b)Si_(1-b) and the like can be mentioned.

In addition, the magnetization fixed layer 5 may have a synthetic structure composed of an antiferromagnetic layer, a ferromagnetic layer, and a nonmagnetic layer. In the synthetic structure, the magnetization direction is firmly maintained by the antiferromagnetic layer, and therefore, the structure can function as a fixed magnetization layer hardly influenced by the outside environment.

Furthermore, when the magnetization direction of the magnetization fixed layer 5 is made perpendicular to the laminated surface, it is preferable to use a laminated film of Co and Pt. In particular, the magnetization fixed layer 5 can be [Co(0.24 nm)/Pt(0.16 nm)]₆/Ru(0.9 nm)/[Pt(0.16 nm)/Co(0.16 nm)]₄/Ta(0.2 nm)/FeB(1.0 nm).

The magnetization of the magnetization fixed layer 5 is fixed in one direction and the magnetization direction of the magnetic wall driving layer 1 (more precisely, the portion 1 cA sandwiched between the lower electrode layer 4 and the magnetization fixed layer 5 as well as the nonmagnetic layer 6) is changed relatively so that they function as the magnetoresistance effect element portion 10. As a method of magnetization of the magnetization fixed layer 5, a known method can be used. When used as a coercive force difference type (pseudo spin valve type) MRAM, the coercive force of the magnetization fixed layer is greater than the coercive force of the magnetic wall driving layer 1. In addition, when used as an exchange bias type (spin valve type) MRAM, the magnetization direction of the magnetization fixed layer 5 is fixed by exchange coupling with the antiferromagnetic layer.

The magnetoresistance effect element portion 10 has a role of a tunneling magneto-resistance (TMR) element when the nonmagnetic layer 6 is made of an insulator and has a role of a giant magnetoresistive (GMR) element when the nonmagnetic layer 6 is made of a metal.

As a material of the nonmagnetic layer 6, a known material that can be used for a nonmagnetic layer can be used

For example, in the case where the nonmagnetic layer 6 is made of an insulator (in the case of a tunnel barrier layer), Al₂O₃, SiO₂, MgO, MgAl₂O₄, ZnAl₂O₄, MgGa₂O₄, ZnGa₂O₄, MgIn₂O₄, ZnIn₂O₄, and a multilayer film or a mixed composition film or the like of these materials can be used. In addition to the materials, a material and the like in which a portion of Al, Si, or Mg is substituted with Zn, Be or the like can also be used. Among them, since MgO and MgAl₂O₄ are materials that can realize coherent tunneling, spins can be efficiently injected

When the nonmagnetic layer 6 is made of a metal, Cu, Au, Ag, or the like can be used as the material thereof.

As shown in FIG. 11, a magnetic coupling layer 8 may be provided between the magnetic wall driving layer 1 and the nonmagnetic layer 6. The main function of the domain wall driving layer 1 is a layer for driving the magnetic wall, and it is not always possible to select a material suitable for the magnetoresistance effect generated via the magnetization fixed layer 5 and the nonmagnetic layer 6. In general, it is known that a ferromagnetic material having a BCC structure is suitable for the magnetization fixed layer 5 and the magnetic coupling layer 8 in order to generate a coherent tunneling effect using the nonmagnetic layer 6. In particular, it is known that as a material of the magnetization fixed layer 5 and the magnetic coupling layer 8, a large output can be obtained when a material having a composition of Co—Fe—B is formed by sputtering.

As shown in FIG. 12, the thickness of the portion of the magnetic wall driving layer 1 which overlaps with the magnetization fixed layer 5 in plan view may be thicker than the other portions. As the magnetic wall transfers over the lower portion of the nonmagnetic layer 6, the cross-sectional area of the magnetic wall increases, so the current density decreases and the drive speed of the magnetic wall slows down. This makes it easy to control the analog value of the output. In addition, in the case of forming such a structure, it is possible to form the magnetic wall driving layer 1, the nonmagnetic layer 6, and the magnetization fixed layer 5 by continuous film formation and scraping unnecessary portions. When the continuous film formation is performed, the bonds between the layers to be joined are strengthened, and the magnetic coupling and the output with higher efficiency can be obtained.

As the magnetoresistance effect element portion 10 included in the present embodiment, a structure of a well-known magnetoresistance effect element can be used. For example, each layer may have a plurality of layers or another layer such as an antiferromagnetic layer for fixing the magnetization direction of the magnetization fixed layer 5.

The shape of the lower electrode layer 4 is preferably the same size as the magnetization fixed layer 5 in plan view so as not to generate a horizontal component of a reading current (spin polarized current) leading to shift of the magnetic wall. However, even if it is not the same size, it exhibits its effect as compared with the conventional magnetic wall driving magnetoresistive effect element. For example, in plan view, the overlapping degree between the lower electrode layer 4 and the magnetization fixed layer 5 is preferably 50% or more, more preferably 90% or more, and further preferably 100%.

For example, if the overlapping degree between the lower electrode layer 4 and the magnetization fixed layer 5 is other than 100%, the magnetic wall may shift during reading. Whether or not the magnetic wall shifts during readout depends on the overlapping position of the lower electrode layer 4 and the magnetization fixed layer 5 and the direction of the read current.

As the material of the lower electrode layer 4, a known material used as an electrode material can be used. For example, aluminum, silver, copper, gold, or the like can be used.

When the high resistance layer 7 is an insulating material, the thickness of the high resistance layer 7 is preferably set to 0.8 nm or more so that the write current does not flow into the lower electrode layer 4. On the other hand, from the viewpoint that the write current does not flow into the lower electrode layer 4 and the influence in the read operation is almost negligible, it is preferable to set the thickness to 2 nm or less.

As a material of the high resistance layer 7, if a layer is capable of suppressing (substantially preventing) the current for driving the magnetic wall to the lower electrode layer 4 when driving the magnetic wall of the magnetization wall driving layer 1, there is no particular limitation. The high resistance layer 7 may be a tunnel barrier layer or a known insulating material that can be used for the tunnel barrier layer may be used. For example, Al₂O₃, SiO₂, MgO, MgAl₂O₄ or the like can be used. In addition to these materials, a material in which a portion of Al, Si, Mg is substituted with Zn, Be or the like can also be used. The material of the high resistance layer 7 functions if the resistivity is at least higher than that of the magnetization wall driving layer 1. For example, a semiconductor such as Si, SiGe or Ge, or a metal such as bismuth or nichrome may be used.

The distance between the end portion in the X direction of the magnetization fixed layer 5 and the end portion in the X direction of the first magnetization supply layer 2 and the second magnetization supply layer 3 can be arbitrarily designed. The magnetic wall in the magnetic wall driving layer 1 has the end portion close to the magnetization fixed layer 5 in contact with the first magnetization supply layer 2 and the second magnetization supply layer 3 to be the maximum movable range. The first magnetization supply layer 2 and the second magnetization supply layer 3 are magnetically coupled to the magnetic wall driving layer 1 and even if the magnetic wall driving operation is performed, when the energization in the magnetic wall driving layer 1 is stopped, the magnetic wall can be stabilized at the end portion thereof. In addition, the readout output is not affected until the magnetic wall shifts from the end portion to the end of the magnetization fixed layer 5.

(Magnetic Wall Utilizing Analog Memory)

The magnetic wall utilization analog memory of the present embodiment includes a plurality of magnetic wall utilization-analog memory elements of the present embodiment.

FIG. 9 is a schematic cross-sectional view of the main portion of the cell in the magnetic wall utilization analog memory.

In the magnetic wall utilization-analog memory element 100 shown in FIG. 1 and the like, the first wiring 11 and the second wiring 12 are connected to the first magnetization supply layer 2 and the second magnetization supply layer 3, respectively. In addition, the magnetization fixed layer 5 is connected to the third wiring 13, and the lower electrode layer 4 is connected to the fourth wiring 14. Reference symbol 15 is an interlayer insulating layer.

FIG. 10 is a diagram schematically showing an example of a circuit structure of the magnetic wall utilization analog memory 1000 according to one embodiment of the present embodiment.

The first control element 15 is connected to the magnetic wall driving layer 1 via the second wiring 12 of each of the plurality of magnetic wall utilization-analog memory elements 100. In addition, the first control element 15 is connected to an external power source which is not shown, and controls the current flowing through the magnetic wall driving layer 1.

The first cell selection element 16 is connected to the magnetic wall driving layer 1 via the first wiring 11 of each of the plurality of magnetic wall utilization-analog memory elements 100. One first cell selection element 16 is provided for one magnetic wall utilization-analog memory element 100. The first cell selection element 16 controls which magnetic wall utilization-analog memory element 100 is to flow a write current. The first cell selection element 16 is grounded.

The second control element 17 is connected to the third wiring 13.

The second control element 17 is connected to an external power supply which is not shown and controls the current flowing through the third wiring 13.

The second cell selection element 18 is connected to the lower electrode layer 4 via the respective fourth wirings 14 of the plurality of magnetic wall utilization-analog memory elements 100. One second cell selection element 18 is provided for one magnetic wall utilization-analog memory element 100. The second cell selection element 18 controls which magnetic wall utilization-analog memory element 100 is to flow the read current. The second cell selection element 18 is grounded.

Known switching elements can be used for the first control element 15, the second control element 17, the first cell selection element 16, and the second cell selection element 18. For example, a transistor element and the like such as a field effect transistor or the like can be used.

As the first wiring 11, the second wiring 12, the third wiring 13, and the fourth wiring 14, a material used as a material of an ordinary wiring can be used. For example, aluminum, silver, copper, gold, or the like can be used.

Hereinafter, with reference to FIG. 10, a writing operation and a reading operation by the magnetic wall utilization analog memory 1000 will be described.

The write operation is controlled by the first control element 15 and the first cell selection element 16.

First, the first control element 15 is opened (connected), and the first cell selection element 16 to be opened is selected. The first control element 15 is connected to an external power supply, and the first cell selection element 16 is grounded. Therefore, the write current flows in the order of the first control element 15, the second wiring 12, the second magnetization supply layer 3, the magnetic wall driving layer 1, the first wiring 11, and the selected first cell selection element 16. Descriptions of the case of flow of the current being in reverse will be omitted.

The reading operation is controlled by the second control element 17 and the second cell selection element 18.

First, the second control element 17 is opened (connected), and the second cell selection element 18 to be opened is selected. The second control element 17 is connected to an external power supply, and the second cell selection element 18 is grounded. Therefore, the write current flows in the order of the second control element 17, the third wiring 13, the magnetization fixed layer, the nonmagnetic layer 6, the magnetic wall driving layer 1, the lower electrode layer 4, and the selected second cell selection element 18. Descriptions of the case of flow of the current being in reverse will be omitted.

The second control element 17 and the second cell selection element 18 function as a reading mechanism.

In the magnetic wall utilization analog memory of the present embodiment, a bipolar element may be connected to either one of the first magnetization supply layer 2 and the second magnetization supply layer 3. With such a configuration, it is possible to shift the magnetic wall in an arbitrary direction by changing the direction of the current.

Regarding the magnetic wall utilization-analog memory element and the magnetic wall utilization analog memory of the present embodiment, when comparing with a conventional magnetic wall driving magnetoresistive effect element and a magnetic wall driving magnetic memory having such a magnetoresistive effect element in each cell, the only difference in the main structure is having the lower electrode layer (and the tunnel barrier layer), and they can be manufactured by a known manufacturing method.

(Nonvolatile Logic Circuit)

The nonvolatile logic circuit of the present embodiment includes the magnetic wall utilization analog memory in which the magnetic wall utilization-analog memory element of the present embodiment is arranged in an array and an STT-MRAM, and has a memory function and a logic function. As the memory function, the magnetic wall utilization analog memory and the STT-MRAM are provided.

Since the magnetic wall utilization analog memory and the STT-MRAM can be manufactured by the same process, the cost can be reduced. Also, by installing the digital STT-MRAM in the same circuit as the magnetic wall utilization analog memory arranged in an array form, the input/output can be digitized and the logic can be formed that can be processed internally in analog is formed.

(Magnetic Neuro Element)

FIG. 13 is a schematic cross-sectional view of an example of a magnetic neuro element according to an embodiment of the present embodiment.

The magnetic neuro element of the present embodiment includes the magnetic wall utilization-analog memory element of the present embodiment, and the third region 1 c of the magnetic wall driving layer 1 includes a first memory portion 21 b, and the second memory portion 21 a and a third memory portion 21 c sandwiching the first memory portion 21 b therebetween, and the portions are arranged side-by-side in the longitudinal direction. In addition, the magnetic neuro element includes a current source (not shown) having a control circuit which is controllable of a flow of a write current capable of shifting magnetic walls sequentially such that the magnetic walls remain in all the memory portions of the first memory portion 21 b, the second memory portion 21 a, and the third memory portion 21 c at least once.

The first memory portion 21 b is a portion of the third region 1 c of the magnetic wall driving layer 1, that overlaps with the magnetization fixed layer 5 in plan view, the second memory portion 21 a is a portion between the magnetization fixed layer 5 and the first magnetization supply layer 2 in plan view (portion not overlapping with the magnetization fixed layer 5 and the first magnetization supply layer 2), and the third memory portion 21 c is a portion between the magnetization fixed layer 5 and the second magnetization supply layer 3 (portion not overlapping with the magnetization fixed layer 5 and the second magnetization supply layer 3).

The magnetic wall utilization-analog memory element of the present embodiment can be used as a magnetic neuro element which is an element simulating the operation of a synapse. In the synapse, it is preferable to have a linear output against external stimuli. Also, when the reversed load is applied, preferably, the synapse is reversed without hysteresis. As shown in FIG. 8, the area of a portion where the magnetization directions of the magnetization fixed layer 5 and the magnetic wall driving layer 1 are parallel is continuously changed by driving (shifting) the magnetic wall. That is, a parallel circuit is formed by the area of the portion where the magnetization directions of the magnetization fixed layer 5 and the magnetic wall driving layer 1 are parallel and the area of the portion where the magnetization directions of the magnetization fixed layer 5 and the magnetic wall driving layer 1 are antiparallel to each other. The horizontal axis of FIG. 8 can be regarded as the driving distance of the magnetic wall, and can exhibit a relatively linear resistance change. Since the driving of the magnetic wall can be driven depending on the magnitude of the current and the time of the applied current pulse, the magnitude and direction of the current and the time of the applied current pulse can be regarded as the external load.

(Initial Memory Stage)

For example, when the magnetic wall of the magnetic wall driving layer 1 is maximally shifted in the −X direction, the magnetic wall is stabilized at the end 21 aA on the magnetization fixed layer 5 side of the first magnetization supply layer 2. When a current is made to flow from the second magnetization supply layer 3 to the first magnetization supply layer 2, electrons flow from the first magnetization supply layer 2 to the second magnetization supply layer 3, and spin-polarized electrons at the inside of the first magnetization supply layer 2 and the magnetic wall driving layer 11 cause spin transfer to the magnetic wall, and the magnetic wall shifts in the +X direction. The readout resistance does not change even if the magnetic wall shifts until the magnetic wall reaches the end 21 aB on the side of the first magnetization supply layer 2 of the magnetization fixed layer 5. This state can be called the initial memory stage. In other words, the case where the magnetic wall is arranged in the second memory portion 21 a can be called an initial memory stage. In the initial memory stage, the data is not recorded; however, the data is ready to be recorded.

(Main Memory Phase)

While the magnetic wall passes through the lower portion (the portion overlapping in plan view) of the magnetization fixed layer 5, the resistance at the time of readout changes as shown in FIG. 8. The current is supplied from the second magnetization supply layer 3 to the first magnetization supply layer 2, so that a load from the outside is obtained, and at the time of reading, a resistance change which is substantially proportional to the load is obtained. This is the main memory stage. That is, the case where the magnetic walls are arranged in the first memory portion 21 b can be called the memory main memory stage. The state in which the magnetic wall is outside the end portion of the magnetization fixed layer 5 can be defined as stored or not stored, and the state where the magnetic wall is outside the end portion of the magnetization fixed layer 5 on the opposite side is can be defined as not stored or stored. Needless to say, if the current flowing between the second magnetization supply layer 3 and the first magnetization supply layer 2 is reversed, the opposite action is obtained.

(Deepening Memory Phase)

Even when the magnetic wall reaches the end 21 cB on the side of the second magnetization supply layer 3 of the magnetization fixed layer 5 and shifts in the direction away from the magnetization fixed layer 5, the output at the time of reading does not change. However, after the magnetic wall is separated from the magnetization fixed layer 5, the output at the time of reading does not change until the magnetic wall reaches the end portion 21 cB of the magnetization fixed layer 5 even if a reverse load is applied. That is, it means that the memory will not be lost even if the external load is given, and this can be called the memory deepening stage. That is, it means that memory will not be lost even if an external load is given, and this can be called the memory deepening stage. That is, the case where the magnetic walls are arranged in the third memory portion 21 c can be called the memory deepening stage.

When the current flowing between the second magnetization supply layer 3 and the first magnetization supply layer 2 is reversed, the correspondence between the initial memory stage, the main memory stage, and the memory deepening stage, and each memory portion is reversed.

In order to obtain the magnetic neuro element of the present embodiment by using the magnetic wall utilization-analog memory element of the present embodiment as an element simulating the operation of a synapse, it is necessary to provide a current source capable of applying a write current such that the shift of the magnetic wall sequentially passes through the steps from the initial memory stage, the main memory stage, and the memory deepening stage. The magnetic neuro element includes a current source (not shown) having a control circuit which is controllable of a flow of a write current capable of shifting magnetic walls sequentially such that the magnetic walls remain in all the memory portions of the first memory portion, the second memory portion, and the third memory portion at least once.

Depending on the condition of the write current, it is possible to determine how many times the magnetic wall passes through each of the first memory portion, the second memory portion, and the third memory portion.

(Memory Oblivion Phase)

Memory can be forgotten by shifting the magnetic wall of the magnetic wall driving layer 1 to the non-memory state. In addition, driving and disappearance of the magnetic wall can also be caused by applying external magnetic field, heat, and physical distortion. In the magnetic wall utilization-analog memory element of the present embodiment, since the output shows a constant low resistance value and high resistance value, the memory and non-memory are determined by definition. In addition, in the case where the magnetic wall is shifted or eliminated by a method other than flowing a current to the magnetic wall driving layer 1, due to randomness, the correlation of information between the plurality of magnetic wall utilization-analog memory elements is lost. These can be called the memory oblivion phase.

(Artificial Brain Using Magnetic Neuro Element)

The magnetic neuro element of the present embodiment simulates synaptic movements, and is a memory that can undergo an initial memory stage, a main memory stage, and a memory deepening stage. It is possible to simulate the brain by installing the magnetic wall utilization analog memory of the present embodiment on a plurality of circuits. It is possible to form a brain with a high degree of integration in an arrangement that is evenly arrayed vertically and horizontally like a general memory.

In addition, as shown in FIG. 14, it is possible to form brains with different degrees of recognition from external loads in an arrangement in which a plurality of magnetic neuro elements having specific circuits are arrayed as one block. For example, it is possible to create brain individuality such as a brain with high understanding of languages or a brain with high sensitivity for colors. In other words, by processing information obtained from an external sensor in the five-senses regions optimized for vision, taste, touch, smell, and auditory perception, and further judging in the logical thinking region, it is possible to form a process of determining the next behavior. Further, when the material of the magnetic wall driving layer 1 is changed, the driving speed of the magnetic wall for the load and a method of forming the magnetic wall are changed, so that it is possible to form an artificial brain whose change is the individuality thereof.

DESCRIPTION OF THE REFERENCE SYMBOLS

-   1: magnetic wall driving layer -   1 a: first region -   1 b: second region -   1 c: third region -   2: first magnetization supply layer -   3: second magnetization supply layer -   4: lower electrode layer -   5: magnetization fixed layer -   6: nonmagnetic layer -   7: tunnel barrier layer -   8: magnetic coupling layer -   21 a: second memory portion -   21 b: first memory portion -   21 c: third memory portion -   100: magnetic wall utilization-analog memory element -   1000: magnetic wall utilization analog memory 

The invention claimed is:
 1. A magnetic neuro element comprising: a magnetic wall driving layer comprising a magnetic wall, a first region, a second region, and a third region located between the first region and the second region; and a magnetization fixed layer provided at the third region through a nonmagnetic layer, wherein the magnetic wall moves from the first region to the second region through the third region, or from the second region to the first region through the third region, a change of a resistance value between the magnetic wall driving layer and the magnetization fixed layer simulates a change of a synaptic coupling strength, the magnetic wall driving layer has a magnetic wall pinning portion, a position of the magnetic wall in the magnetic wall driving layer is shifted to a desired position, an analog resistance value can be output as the resistance value varies, the resistance value varies depending on the position of the magnetic wall, a lower electrode layer provided into which a read current flows directly below the magnetization fixed layer, and the read current flows in a vertical direction of a surface of the magnetic wall driving layer.
 2. The magnetic neuro element according to claim 1, further comprising: a higher resistance layer opposite to the magnetization fixed layer of the magnetic wall driving layer and has higher electrical resistivity than the magnetic wall driving layer, wherein a length of the magnetic wall driving layer is 60 nm or more.
 3. The magnetic neuro element according to claim 1, further comprising: a first magnetization supply layer which is in contact with the first region and has a first magnetization direction; a second magnetization supply layer which is in contact with the second region and has a second magnetization direction opposite to the first magnetization direction, wherein the higher resistance layer is Al₂O₃, SiO₂, MgO, MgAl₂O₄, Si, SiGe or Ge.
 4. The magnetic neuro element according to claim 3, wherein a magnetization orientation of each of the magnetic wall driving layer, the first magnetization supply layer, the second magnetization supply layer, and the magnetization fixed layer is parallel to each of the corresponding layers, and the higher resistance layer is Si, SiGe or Ge.
 5. The magnetic neuro element according to claim 3, wherein a bipolar element is connected to either one of the first magnetization supply layer and the second magnetization supply layer, and the bipolar element is configured to change a direction of current.
 6. A magnetic wall utilization analog memory comprising a plurality of the magnetic neuro elements according to claim
 1. 7. The magnetic neuro element according to claim 1, wherein: the third region of the magnetic wall driving layer comprises a first memory portion, and a second memory portion and a third memory portion arranged so as to sandwich the first memory portion therebetween, which are arranged side-by-side in the longitudinal direction; and the magnetic neuro element further comprises a current source having a control circuit which controls a flow of a write current configured to shift magnetic walls sequentially such that the magnetic walls remain in all memory portions of the first memory portion, the second memory portion, and the third memory portion at least once.
 8. The magnetic neuro element according to claim 2, wherein the higher resistance layer is bismuth or nichrome.
 9. A volatile logic circuit comprising: a magnetic wall utilization analog memory on which the magnetic neuro element according to claim 1 and a spin-transfer torque magnetic random-access memory (STT-MRAM) are provided, wherein the magnetic wall utilization analog memory and the STT-MRAM are in a same circuit, and, wherein the circuit has a memory function and a logical function.
 10. A magnetic neuro element comprising: a magnetic wall driving layer comprising a magnetic wall, a first region, a second region, and a third region located between the first region and the second region; and a magnetization fixed layer provided at the third region through a nonmagnetic layer, wherein the magnetic wall moves in the third region, a conductivity that is a reciprocal of a resistance value between the magnetic wall driving layer and the magnetization fixed layer changes linearly with respect to an input signal, the magnetic wall driving layer has a magnetic wall pinning portion, a position of the magnetic wall in the magnetic wall driving layer is shifted to a desired position, an analog resistance value can be output as the resistance value varies, the resistance value varies depending on the position of the magnetic wall, a lower electrode layer provided into which a read current flows directly below the magnetization fixed layer, and the read current flows in a vertical direction of a surface of the magnetic wall driving layer.
 11. The magnetic neuro element according to claim 10, further comprising: a higher resistance layer opposite to the magnetization fixed layer of the magnetic wall driving layer and has higher electrical resistivity than the magnetic wall driving layer, wherein a length of the magnetic wall driving layer is 60 nm or more.
 12. The magnetic neuro element according to claim 10, further comprising: a first magnetization supply layer which is in contact with the first region and has a first magnetization direction; a second magnetization supply layer which is in contact with the second region and has a second magnetization direction opposite to the first magnetization direction, wherein the higher resistance layer is Al₂O₃, SiO₂, MgO, MgAl₂O₄, Si, SiGe or Ge.
 13. The magnetic neuro element according to claim 12, wherein a magnetization orientation of each of the magnetic wall driving layer, the first magnetization supply layer, the second magnetization supply layer, and the magnetization fixed layer is parallel to each of the corresponding layers, and the higher resistance layer is Si, SiGe or Ge.
 14. The magnetic neuro element according to claim 12, wherein a bipolar element is connected to either one of the first magnetization supply layer and the second magnetization supply layer, and the bipolar element is configured to change a direction of current.
 15. A magnetic wall utilization analog memory comprising a plurality of the magnetic neuro elements according to claim
 10. 16. The magnetic neuro element according to claim 10, wherein: the third region of the magnetic wall driving layer comprises a first memory portion, and a second memory portion and a third memory portion arranged so as to sandwich the first memory portion therebetween, which are arranged side-by-side in the longitudinal direction; and the magnetic neuro element further comprises a current source having a control circuit which controls a flow of a write current configured to shift magnetic walls sequentially such that the magnetic walls remain in all memory portions of the first memory portion, the second memory portion, and the third memory portion at least once.
 17. The magnetic neuro element according to claim 11, wherein the higher resistance layer is bismuth or nichrome.
 18. A volatile logic circuit comprising: a magnetic wall utilization analog memory on which the magnetic neuro element according to claim 10 and a spin-transfer torque magnetic random-access memory (STT-MRAM) are provided, wherein the magnetic wall utilization analog memory and the STT-MRAM are in a same circuit, and, wherein the circuit has a memory function and a logical function. 